1. Field of the Invention
The present invention relates to a grommet which is inserted into a through-hole having a burring of a vehicle body panel.
2. Description of Related Art
Generally, a vehicle body panel includes a through-hole which allows insertion of a wire harness, the panel dividing an engine compartment and an inner vehicle space. In such a case, an elastic member such as rubber, elastomer or the like (hereafter referred to as grommet) is fitted into the through-hole to secure a sufficient waterproofing condition between the through-hole and the wire harness. The grommet has a structure to secure a waterproof condition, including a grommet body and a resin inner mounted on the grommet body. The grommet provides protection for the wire harness and divides the interior and exterior sides of the vehicle body panel with respect to the through-hole (see Japanese Utility Patent Laid-open Publication H5-91997).
Normally, the through-hole formed on the vehicle body panel includes a through-hole formed simply by punching, in addition to a through-hole having a protruding burring, by bending an opening edge of the through-hole into one side. When the grommet is fitted into such a through-hole having a burring, the grommet is inserted from a side where the burring does not protrude therefrom, and a burring engagement piece formed on a tip of the resin inner is brought to engage with a tip of the burring (see Japanese Patent Laid-open Publication 2012-130085).
Specifically, as shown in FIG. 5, a grommet 100 is formed to have a grommet body 101 made of rubber or elastomer, which is assembled to a resin inner 102 made of a resin molding article. A wire harness 200 which is inserted into the grommet 100 is fixated to the grommet body 101 by an adhesive tape T, for example.
The grommet body 101 has a conically-protruding conical flange portion 103. The conical flange portion 103 includes a main body 103a and a tip portion 103b. The main body 103a expands at a predetermined inclined angle of θ1 from a horizontal position of the figure. The tip portion 103b has an inclined angle θ2 of substantially 90 degrees, which is bigger than the inclined angle θ1 (θ2>θ1). On an inner surface side of the conical flange portion 103, a first seal lip 104 protrudes around the entire circumference near the boundary between the main body 103a and the tip portion 103b, and a second seal lip 105 protrudes around the entire circumference near an opening edge of the main body 103a. 
The resin inner 102 includes a cylinder portion 106 into which the wire harness 200 is inserted, a burring engagement piece 107 for engaging with a burring B of a vehicle body panel P (discussed below) and being formed on one end of the cylinder portion 106, and a flange portion 108 that is formed on the other end of the cylinder portion 106 and is fitted with an inward opening engagement groove portion 101a, which is formed on the grommet body 101.
FIG. 6 is an enlarged view in cross-section of a main part which illustrates a state where the burring engagement piece 107 of the grommet 100 contacting the tip of the burring B of the vehicle body panel P. In this case, the grommet 100 is inserted into a through-hole H of the vehicle body panel P from a lower side as indicated in the figure, and after an opening edge of the conical flange portion 103 contacts a first surface of the vehicle body panel P, the conical flange portion 103 moves outward by additional insertion. More specifically, in a state where the inclined angle θ1 of the main body 103a and the inclined angle θ2 of the tip portion 103b are both smaller, the first seal lip 104 and the second seal lip 105 press firmly onto the first surface of the vehicle body panel P.
However, a worker operates with one hand inside a narrow work space of the engine compartment that is outside of the inner vehicle space, when the grommet 100, into which the wire harness 200 is inserted, is fitted onto the through-hole H having the burring B of the vehicle body panel P. In other words, the worker is forced to fit the grommet 100 into the through-hole H by touch without visual observation.
For this reason, a part of or the entire conical flange portion 103 sometimes becomes buckled down inwardly depending on an insertion angle or the like of the grommet 100 with respect to the through-hole H, when the grommet 100 contacts the first surface of the vehicle body panel P.
As shown in FIG. 7, for instance, the tip portion of 103b at the inclined angle θ2 contacts the first surface of the vehicle body panel P in a substantially vertical state, when the conical flange portion 103 comes to a close contact with the vehicle body panel P after the resin inner 102 is inserted into the through-hole H.
Because of this, in a situation when the worker performs insertion by touch with an improper insertion angle of the resin inner 102, the opening edge of the conical flange portion 103 becomes bent inwardly and the entire conical flange portion 103 becomes buckled down. Therefore, a proper contact pressure is not provided against the vehicle body panel P, as shown in FIG. 7. As a result, there was a circumstance where a sufficient waterproof condition is not provided between the engine compartment and the inner vehicle space.